Composition for window film, flexible window film manufactured using the same and flexible display including the same

ABSTRACT

A composition for a window film includes a siloxane resin represented by Formula 1, and an initiator. A flexible window film is manufactured using the same, and has a pencil hardness of about 7H or higher, a radius of curvature of about 5.0 mm or lower, and a difference in yellow index before and after irradiation (ΔY.I.) of about 5.0 or less. A flexible display includes the flexible window film. 
       (R 1 SiO 3/2 ) x (R 2 R 3 SiO 2/2 ) y   Formula 1

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2014-0170878, filed on Dec. 2, 2014 in the KoreanIntellectual Property Office, the entire content of which isincorporated herein by reference.

BACKGROUND

1. Technical Field

Embodiments of the present invention relate to a composition for awindow film, a flexible window film manufactured using the same, and aflexible display including the same.

2. Description of the Related Art

Recently, glass substrates (or high-hardness substrates) in displays arebeing replaced by films in order to develop flexible displays capable ofbeing folded and unfolded. Since the flexible displays are thin andlightweight, and can be folded and unfolded, these flexible displays canbe manufactured into various shapes.

For the flexible displays, various devices and substrates includedtherein are also required to have flexibility. In particular, since thewindow film is disposed at the outermost side of the flexible display,the window film is required to have flexibility, high hardness, andoptical reliability.

SUMMARY

In accordance with embodiments of the present invention, a compositionfor a window film may include: a siloxane resin represented by Formula1, and an initiator.

(R¹SiO_(3/2))_(x)(R²R³SiO_(2/2))_(y)  Formula 1

In Formula 1, R¹, R² and R³ are as defined in the following detaileddescription; and 0<x<1, 0<y<1, and x+y=1.

In accordance with embodiments of the present invention, a flexiblewindow film may include a base layer and a coating layer formed on onesurface of the base layer. The coating layer may be formed of thecomposition for a window film as set forth herein.

In accordance with embodiments of the present invention, a flexibledisplay may include the flexible window film as set forth herein.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view of a flexible window filmaccording to embodiments of the present invention.

FIG. 2 is a schematic cross-sectional view of a flexible window filmaccording to embodiments of the present invention.

FIG. 3 is a partial cross-sectional view of a flexible display accordingto embodiments of the present invention.

FIG. 4 is a partial cross-sectional view of a display unit (according toembodiments of the present invention) of the flexible display of FIG. 3.

FIG. 5 is a partial cross-sectional view of a flexible display accordingto embodiments of the present invention.

FIG. 6 is a partial cross-sectional view of a flexible display accordingto embodiments of the present invention.

DETAILED DESCRIPTION

Exemplary embodiments of the present invention are described in detailwith reference to the accompanying drawings. It is understood that thepresent invention is not limited to the following embodiments and may beembodied in different ways. In the drawings, portions irrelevant to thedescription are omitted for clarity. Like components are denoted by likereference numerals throughout the specification.

As used herein, spatially relative terms such as “upper side” and “lowerside” are defined with reference to the accompanying drawings. Thus, itis understood that the term “upper side” can be used interchangeablywith the term “lower side”. It is understood that when an element suchas a layer, film, region or substrate is referred to as being placed“on” another element, it can be placed directly on the other element, orintervening layer(s) may be present. On the other hand, when an elementis referred to as being placed “directly on” another element,intervening layer(s) are not present.

Herein, “pencil hardness” is measured on a coating layer of a windowfilm using a pencil hardness tester (Heidon Co., Ltd.) in accordancewith JIS K5400. In measuring pencil hardness, pencils (Mitsubishi Co.,Ltd.) having a pencil hardness of 6B to 9H are used. Specifically,pencil hardness is measured under a load of 1 kg on the coating layer, ascratching angle of 45°, and a scratching speed of 60 mm/min. When thecoating layer has one or more scratches after being tested 5 times usinga certain pencil, the pencil hardness is measured again using anotherpencil having a hardness one-level lower than the previous pencil. Themaximum pencil hardness value of the pencil that allows no scratches tobe observed all five times on the coating layer is taken as the pencilhardness of the coating layer after pencil hardness is repeatedlymeasured five times.

As used herein, the term “radius of curvature” refers to the minimumradius of the jig that causes no cracks on a window film specimensubjected to radius of curvature testing. In particular, the radius ofcurvature test involves winding the window film specimen (having a sizeof 3 cm×15 cm (width×length)) around the jig (CFT-200R, COVOTECH Co.,Ltd.), keeping it wound for 5 seconds, unwinding, and then observingwith the naked eye whether the specimen suffers from cracking. Here, theradius of curvature in the compressive direction is measured when thespecimen is wound around the jig such that the coating layer of thewindow film contacts the surface of the jig. The radius of curvature inthe tensile direction is measured when the specimen is wound around thejig such that the base layer of the window film contacts the jig. Here,the window film specimen may have a thickness of 50 μm to 300 μm.

As used herein, the term “ΔY.I.” refers to the difference in the yellowindex (Y2-Y1) before and after light irradiation. Measurement of theyellow index (Y1) is done under a D65 light source and 2° angle betweenthe window coating layer and the light source using a colorimeter(CM3600D, Konica Minolta). After measuring the yellow index (Y1), thewindow film is irradiated with light at a peak wavelength of 306 nm for72 hours using a light resistance tester (Xe-1, Q-sun Co., Ltd.), andthen the yellow index (Y2) is measured in the same manner as the yellowindex (Y1).

As used herein, the term “(meth)acryl” refers to acryl and/or methacryl.

Unless otherwise stated, the term “substituted” as used herein meansthat at least one hydrogen atom of the functional group is substitutedwith a hydroxyl group, an unsubstituted C₁ to C₁₀ alkyl group, a C₁ toC₁₀ alkoxy group, a C₃ to C₁₀ cycloalkyl group, a C₆ to C₂₀ aryl group,a C₇ to C₂₀ arylalkyl group, a benzophenone group, a C₁ to C₁₀ alkylgroup-substituted C₆ to C₂₀ aryl group, or a C₁ to C₁₀ alkoxygroup-substituted C₁ to C₁₀ alkyl group.

As used herein, the term “crosslinkable functional group” refers tofunctional groups crosslinked by heat and/or light. For example, thecrosslinkable group may refer to an epoxy group, an epoxygroup-containing group, a glycidyl group, a glycidyl group-containinggroup, a glycidoxy group, a glycidoxy group-containing group, anoxetanyl group, an oxetanyl group-containing group, or the like. In someembodiments, the crosslinkable group may refer to an epoxy group; aglycidyl group; a glycidoxy group; an oxetanyl group; an oxetanyloxygroup; a C₁ to C₂₀ alkyl group having an epoxy group, glycidyl group,glycidoxy group, epoxidized C₅ to C₂₀ cycloalkyl group, epoxidized C₁ toC₁₀ alkyl group, oxetanyl group, or oxetanyloxy group; or a C₅ to C₂₀cycloalkyl group having an epoxy group, glycidyl group, glycidoxy group,epoxidized C₅ to C₂₀ cycloalkyl group, epoxidized C₁ to C₁₀ alkyl group,oxetanyl group, or oxetanyloxy group. The “crosslinkable functionalgroup” may be substituted or unsubstituted.

As used herein, the symbol “Ec” represents a (3,4-epoxycyclohexyl)ethylgroup, the symbol “Me” represents a methyl group, the symbol “Gp”represents a 3-glycidoxypropyl group, and the symbol “Op” represents a3-oxetanylpropyl group.

As used herein, the term “halogen” refers to fluorine, chlorine,bromine, or iodine.

According to embodiments of the present invention, a composition for awindow film may include: a siloxane resin represented by Formula 1; andan initiator.

(R¹SiO_(3/2))_(x)(R²R³SiO_(2/2))_(y)  Formula 1

In Formula 1, R¹ is a crosslinkable functional group. R² and R³ are eachindependently hydrogen, a crosslinkable functional group, anunsubstituted or substituted C₁ to C₂₀ alkyl group, or an unsubstitutedor substituted C₅ to C₂₀ cycloalkyl group. At least one of R² and R³ isan unsubstituted or substituted C₁ to C₂₀ alkyl group. Also, 0<x<1,0<y<1, and x+y=1.

The composition for a window film according to embodiments includes thesiloxane resin represented by Formula 1, thereby improving the hardnessand flexibility of the window film. In addition, the siloxane resinrepresented by Formula 1 is prepared by adjusting the proportions ofeach of the silicone monomers, i.e., (R¹SiO_(3/2)) and (R²R³SiO_(2/2)),thereby enabling adjustment of the hardness and flexibility of thewindow film. For example, x and y may be about 0.20 to about 0.999 andabout 0.001 to about 0.80, respectively. For example, x and y may beabout 0.20 to about 0.99 and about 0.01 to about 0.80, respectively. Insome embodiments, for example, x and y may be about 0.80 to about 0.99and about 0.01 to about 0.20, respectively. Within these ranges, thewindow film can have good hardness and flexibility. For example, when xis about 0.80 to about 0.99 and y is about 0.01 to about 0.20, thewindow film (having a polyester film (such as a polyimide film, apolyethylene terephthalate film or the like) as the base layer) can havebetter flexibility and optical reliability.

R¹ in Formula 1 can provide crosslinkability to the composition for awindow film. In some embodiments, R¹ may include(3,4-epoxycyclohexyl)methyl, (3,4-epoxycyclohexyl)ethyl,(3,4-epoxycyclohexyl)propyl, 3-glycidoxypropyl, 3-oxetanylmethyl,3-oxetanylethyl, 3-oxetanylpropyl, 3-oxetanyloxy groups, and/or thelike.

R² and R³ in Formula 1 can provide crosslinkability and flexibility tothe composition for a window film. In some embodiments, R² may be anunsubstituted or substituted C₁ to C₂₀ alkyl group, and R³ may be acrosslinkable functional group. Accordingly, crosslinkability of thecomposition for a window film can be further improved, thereby furtherimproving the hardness of the window film. In some embodiments, forexample, R² and R³ may each independently include(3,4-epoxycyclohexyl)methyl, (3,4-epoxycyclohexyl)ethyl,(3,4-epoxycyclohexyl)propyl, glycidoxy propyl, methyl, ethyl groups,and/or the like.

In some embodiments, the siloxane resin represented by Formula 1 mayinclude a compound represented by any one of Formulae 1-1 to 1-18, butthe siloxane resin is not limited thereto.

(EcSiO_(3/2))_(x)(EcMeSiO_(2/2))_(y)  Formula 1-1

(EcSiO_(3/2))_(x)((Me)₂SiO_(2/2))_(y)  Formula 1-2

(EcSiO_(3/2))_(x)(GpMeSiO_(2/2))_(y)  Formula 1-3

(GpSiO_(3/2))_(x)(EcMeSiO_(2/2))_(y)  Formula 1-4

(GpSiO_(3/2))_(x)((Me)₂SiO_(2/2))_(y)  Formula 1-5

(GpSiO_(3/2))_(x)(GpMeSiO_(2/2))_(y)  Formula 1-6

(OpSiO_(3/2))_(x)(EcMeSiO_(2/2))_(y)  Formula 1-7

(OpSiO_(3/2))_(x)((Me)₂SiO_(2/2))_(y)  Formula 1-8

(OpSiO_(3/2))_(x)(GpMeSiO_(2/2))_(y)  Formula 1-9

In Formulae 1-1 through 1-9, 0<x<1, 0<y<1, and x+y=1.

(EcSiO_(3/2))_(x)(EcMeSiO_(2/2))_(y1)((Me)₂SiO_(2/2))_(y2)  Formula 1-10

(GpSiO_(3/2))_(x)(EcMeSiO_(2/2))_(y1)((Me)₂SiO_(2/2))_(y2)  Formula 1-11

(OpSiO_(3/2))_(x)(EcMeSiO_(2/2))_(y1)((Me)₂SiO_(2/2))_(y2)  Formula 1-12

(EcSiO_(3/2))_(x)(GpMeSiO_(2/2))_(y1)((Me)₂SiO_(2/2))_(y2)  Formula 1-13

(GpSiO_(3/2))_(x)(GpMeSiO_(2/2))_(y1)((Me)₂SiO_(2/2))_(y2)  Formula 1-14

(OpSiO_(3/2))_(x)(GpMeSiO_(2/2))_(y1)((Me)₂SiO_(2/2))_(y2)  Formula 1-15

(EcSiO_(3/2))_(x)(EcMeSiO_(2/2))_(y1)(GpMeSiO_(2/2))_(y2)  Formula 1-16

(GpSiO_(3/2))_(x)(EcMeSiO_(2/2))_(y1)(GpMeSiO_(2/2))_(y2)  Formula 1-17

(OpSiO_(3/2))_(x)(EcMeSiO_(2/2))_(y1)(GpMeSiO_(2/2))_(y2)  Formula 1-18

In Formulae 1-10 through 1-18, 0<x<1, 0<y1<1, 0<y2<1, and x+y1+y2=1. Insome embodiments, in Formulae 1-10 to 1-18, x and y1+y2 may be about0.20 to about 0.999 and about 0.001 to about 0.80, respectively. Forexample, in some embodiments, x and y1+y2 may be about 0.20 to about0.99 and about 0.01 to about 0.80, respectively. In some embodiments, xand y1+y2 may be about 0.80 to about 0.99 and about 0.01 to about 0.20,respectively. Within these ranges, the window film can have goodhardness and flexibility.

The siloxane resin represented by Formula 1 may have a weight averagemolecular weight of about 4,000 to about 100,000, for example about4,500 to about 10,000, about 5,000 to about 8,000, or about 5,000 toabout 7,000. Within these ranges, the siloxane resin can be easilyprepared and provide good hardness and flexibility to the window film.

The siloxane resin represented by Formula 1 may have a polydispersityindex (PDI) of about 1.0 to about 3.0, for example about 1.5 to about2.5. Within these ranges, the composition for a window film can exhibitgood coatability and stable coating properties.

The siloxane resin represented by Formula 1 may have an epoxy equivalentof about 0.1 mol/100 g to about 1.0 mol/100 g, for example about 0.3mol/100 g to about 0.7 mol/100 g. Within these ranges, the window filmcan exhibit stable coating properties.

The initiator can cure the crosslinkable functional group of thesiloxane resin represented by Formula 1. The initiator may include atleast one of a cationic photo initiator and/or a radical photoinitiator. A single one of these initiators may be used alone, or acombination thereof may be used.

The cationic photo initiator may be any suitable cationic photoinitiator, including those known to those skilled in the art. Forexample, the cationic photo initiator may include an onium saltincluding a cation and an anion. The cation may include: adiaryliodonium, such as diphenyliodonium, 4-methoxydiphenyliodonium,bis(4-methylphenyl)iodonium, bis(4-tert-butylphenyl)iodonium,bis(dodecylphenyl)iodonium, and/or(4-methylphenyl)[(4-(2-methylpropyl)phenyl)iodonium; a triarylsulfonium,such as triphenylsulfonium, and/ordiphenyl-4-thiophenoxyphenylsulfonium;bis[4-(diphenylsulfonio)phenyl]sulfide; and/or the like. In someembodiments, the anion may include hexafluorophosphate (PF₆ ⁻),tetrafluoroborate (BF₄ ⁻), hexafluoroantimonate (SbF₆ ⁻),hexafluoroarsenate (AsF₆ ⁻), hexachioroantimonate (SbCl₆ ⁻), and/or thelike.

The radical photo initiator may be any suitable radical photo initiator,including those known to those skilled in the art. For example, theradical photo initiator may include at least one of thioxanthone,phosphorus, triazine, acetophenone, benzophenone, benzoin, and/or anoxime radical photo initiator.

The initiator may be present in an amount of about 0.01 parts by weightto about 20 parts by weight, for example about 1 part by weight to about10 parts by weight, based on 100 parts by weight of the siloxane resinrepresented by Formula 1. Within these ranges, the siloxane resin can besufficiently cured, and deteriorations in the transparency of the windowfilm due to residual initiator can be prevented or reduced.

The composition for a window film according to the embodiment mayfurther include nanoparticles. The nanoparticles can further improve thehardness of the window film. The nanoparticles may include at least oneof silica, aluminum oxide, zirconium oxide, and/or titanium oxide, butthe nanoparticles are not limited thereto. The nanoparticles may besurface-treated with a silicone compound to improve miscibility with thesiloxane resin. The nanoparticles may have any shape and size withoutlimitation. For example, the nanoparticles may include particles havingcircular, flake, amorphous shapes, or the like. The nanoparticles mayhave an average particle diameter of about 1 nm to about 200 nm, orabout 10 nm to about 50 nm. Within these ranges, the nanoparticles canimprove the hardness of the window film without adversely affecting thesurface roughness and transparency of the window film. The nanoparticlesmay be present in an amount of about 0.1 parts by weight to about 60parts by weight, for example about 10 parts by weight to about 50 partsby weight, based on 100 parts by weight of the siloxane resinrepresented by Formula 1. Within these ranges, the nanoparticles canimprove the hardness of the window film without adversely affecting thesurface roughness and transparency of the window film.

The composition for a window film according to embodiments may furtherinclude an additive. The additive may provide an additional function tothe window film. The additive may include any suitable additive,including those know to those skilled in the art. For example, theadditive may be selected from UV absorbers, reaction inhibitors,adhesion promoters, thixotropic agents, conductivity imparting agents,color regulators, stabilizers, antistatic agents, antioxidants, and/orleveling agents, but the additive is not limited thereto. The reactioninhibitors may include ethynylcyclohexane, the adhesion promoters mayinclude epoxy or alkoxysilyl group-containing silane compounds, and thethixotropic agents may include fumed silica and/or the like. Theconductivity imparting agents may include powders of metals such assilver, copper, aluminum and/or the like, and the color regulators mayinclude pigments, dyes and/or the like.

The UV absorbers can improve the light resistance of the window film.The

UV absorbers may include any suitable UV absorbers, including thoseknown to those skilled in the art. For example, the UV absorbers may beselected from triazine, benzimidazole, benzophenone, benzotriazole,and/or hydroxyphenyltriazine UV absorbers, but the UV absorbers are notlimited thereto.

The additive may be present in an amount of about 0.01 parts by weightto about 5 parts by weight, for example about 0.1 parts by weight toabout 2.5 parts by weight, based on 100 parts by weight of the siloxaneresin represented by Formula 1. Within these ranges, the additive canprovide good hardness and flexibility to the window film while alsorealizing the advantageous effects of the additive.

The composition for a window film according to embodiments may furtherinclude a solvent for facilitating the coating or processing of thecomposition. The solvent may include methylethylketone,methylisobutylketone, and/or propylene glycol monomethyl ether acetate,but is not limited thereto.

The composition for a window film according to embodiments may have aviscosity at 25° C. of about 50 cP to about 2000 cP. Within this range,the composition can facilitate formation of the window film.

According to embodiments of the present invention, a method of preparingthe siloxane resin represented by Formula 1 may include the hydrolysisand condensation of a monomer mixture including a first silicone monomerand a second silicone monomer. The first silicone monomer may be presentin the monomer mixture in an amount of about 20 mol % to about 99.9 mol%, for example about 20 mol % to about 99 mol %, or about 80 mol % toabout 99 mol %. Within these ranges, the first silicone monomer canimprove the hardness and flexibility of the window film. The secondsilicone monomer may be present in the monomer mixture in an amount ofabout 0.1 mol % to about 80 mol %, for example about 1 mol % to about 80mol %, or about 1 mol % to about 20 mol %. Within these ranges, thesecond silicone monomer can improve the hardness and flexibility of thewindow film.

The first silicone monomer may be a silane compound represented byFormula 2. The second silicone monomer may be a silane compoundrepresented by Formula 3. A single one of these silane compounds may beused alone, or a combination thereof may be used.

In Formula 2, R¹ is as defined above in connection with Formula 1, andR⁴, R⁵ and R⁶ are each independently a halogen, a hydroxyl group or a C₁to C₁₀ alkoxy group.

In Formula 3, R² and R³ are as defined above in connection with Formula1, and R⁷ and R⁸ are each independently a halogen, a hydroxyl group or aC₁ to C₁₀ alkoxy group.

In some embodiments, the first silicone monomer may include at least oneof 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane,2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,3-glycidoxypropyltriethoxysilane, 3-oxetanylmethyltrimethoxysilane,3-oxetanylethyltrimethoxysilane, 3-oxetanylpropyltrimethoxysilane,and/or 3-oxetanyloxytrimethoxysilane, but the first silicone monomer isnot limited thereto.

In some embodiments, the second silicone monomer may include at leastone of 2-(3,4-epoxycyclohexyl)ethylmethyldiethoxysilane,dimethyldimethoxysilane, and/or (3-glycidoxypropyl)methyldiethoxysilane,but the second silicone monomer is not limited thereto.

Hydrolysis and condensation of the monomer mixture may be performedaccording any suitable method for preparing a siloxane resin. Hydrolysisof the monomer mixture may include mixing the first silicone monomerwith the second silicone monomer, followed by reacting the siliconemonomers in a mixture of water and at least one of an acid and/or abase. For example, the acid may include a strong acid, for example HClor HNO₃, and the base may include a strong base, for example NaOH, KOHor the like. Hydrolysis of the monomer mixture may be performed at about20° C. to about 100° C. for about 10 minutes to about 7 hours. Theseconditions can improve the efficiency of hydrolysis of the firstsilicone monomer and the second silicone monomer. Condensation of themonomer mixture may be performed at about 20° C. to about 100° C. forabout 10 minutes to about 12 hours under the same conditions as thehydrolysis of the monomer mixture. These conditions can improve theefficiency of condensation of the first silicone monomer and the secondsilicone monomer. A platinum catalyst may further be used to improve theefficiency of hydrolysis and condensation of the monomer mixture. Theplatinum catalyst may be selected from vinylalkylsilane platinumcomplexes including Karstedt catalysts, platinum black, chloroplatinicacid, chloroplatinic acid-olefin complexes, chloroplatinic acid-alcoholcomplexes, and mixtures thereof.

According to some embodiments, a composition for a window film mayinclude a siloxane resin represented by Formula 1, an initiator, and acrosslinking agent. The composition for a window film may furtherinclude the crosslinking agent to improve the degree of crosslinking ofthe window film, thereby improving the hardness of the window film. Thiscomposition for a window film is substantially the same as thecomposition described above except that this composition furtherincludes the crosslinking agent. Therefore, the crosslinking agent willnow be described.

The crosslinking agent contains a crosslinkable functional group,thereby further improving the hardness of the window film. In addition,the proportion of (R²R³SiO_(2/2)) in Formula 1 may be increased toimprove the flexibility of the window film. The crosslinking agent mayfurther include at least one of a non-cyclic aliphatic hydrocarbon, acyclic aliphatic hydrocarbon, an aromatic hydrocarbon, a hydrogenatedaromatic hydrocarbon, and/or an oxetane group, thereby further improvingthe flexibility of the window film.

For example, the crosslinking agent may be selected from non-cyclicaliphatic epoxy monomers, cyclic aliphatic epoxy monomers, aromaticepoxy monomers, hydrogenated aromatic epoxy monomers, oxetane monomers,and combinations thereof. A single crosslinking agent may be used alone,or a combination thereof may be used. The cyclic aliphatic epoxy monomercan further improve the hardness, flexibility and optical reliability ofthe window film (including the siloxane resin represented by Formula 1and a polyester film (such as a polyimide film or a polyethyleneterephthalate film) as the base film).

The non-cyclic aliphatic epoxy monomer may include: 1,4-butanedioldiglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentylglycoldiglycidyl ether, trimethylolpropanetriglycidyl ether,polyethyleneglycol diglycidyl ether, glycerin triglycidyl ether,polypropylene glycol diglycidyl ether; polyglycidyl ethers of polyetherpolyols obtained by adding at least one alkylene oxide to an aliphaticpolyhydric alcohol such as ethylene glycol, propylene glycol, and/orglycerine; diglycidyl esters of aliphatic long-chain dibasic acids;monoglycidyl ethers of aliphatic higher alcohols; glycidyl ethers ofhigher fatty acids; epoxidized soybean oil; butyl epoxystearate; octylepoxy stearate; epoxidized linseed oil; epoxidized polybutadiene; and/orthe like.

The cyclic aliphatic epoxy monomer is a compound in which an alicyclicgroup has at least one epoxy group, and may include alicyclic epoxycarboxylate, alicyclic epoxy (meth)acrylate, and/or the like.Nonlimiting examples of the cyclic aliphatic epoxy monomer may include(3,4-epoxycyclohexyl)methyl-3′,4′-epoxycyclohexanecarboxylate,diglycidyl 1,2-cyclohexanedicarboxylate,epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-meta-dioxane,bis(3,4-epoxycyclohexylmethyl)adipate,bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate,3,4-epoxy-6-methylcyclohexylmethyl-3′,4′-epoxy-6′-methylcyclohexanecarboxylate,6-caprolactone-modified3,4-epoxycyclohexylmethyl-3′,4′-epoxy-cyclohexanecarboxylate,trimethylcaprolactone-modified3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexanecarboxylate,β-methyl-δ-valerolactone-modified3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexanecarboxylate,1,4-cyclohexanedimethanol bis(3,4-epoxycyclohexane)carboxylate, ethyleneglycol di(3,4-epoxycyclohexylmethyl)ether,ethylenebis(3,4-epoxycyclohexanecarboxylate),3,4-epoxycyclohexylmethyl(meth)acrylate, 4-vinylcyclohexenedioxide,vinylcyclohexenemonoxide, and the like.

The aromatic epoxy monomer may be selected from: bisphenol epoxy resinssuch as bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, andbisphenol S diglycidyl ether; novolac epoxy resins such as phenolnovolac epoxy resins, cresol novolac epoxy resins, andhydroxybenzaldehydephenol novolac epoxy resins; polyfunctional epoxyresins such as tetrahydroxyphenylmethaneglycidyl ether,tetrahydroxybenzophenoneglycidyl ether, and epoxidized polyvinyl phenol,and the like.

The hydrogenated aromatic epoxy monomer refers to a monomer obtainedthrough selective hydrogenation of an aromatic epoxy monomer in thepresence of a catalyst under pressure. The aromatic epoxy monomer forthe hydrogenated aromatic epoxy monomer may include the aromatic epoxymonomers set forth above.

Nonlimiting examples of the oxetane monomer may include 3-methyloxetane,2-methyloxetane, 2-ethylhexyloxetane, 3-oxetanol, 2-methyleneoxetane,3,3-oxetanedimethanethiol, 4-(3-methyloxetan-3-yl)benzonitrile, N-(2,2-dimethylpropyl)-3-methyl-3-oxetane methaneamine,N-(1,2-dimethylbutyl)-3-methyl-3-oxetane methaneamine,(3-ethyloxetan-3-yl)methyl(meth)acrylate,4[(3-ethyloxetan-3-yl)methoxy]butan-1-ol,3-ethyl-3-hydroxymethyloxetane, xylenebis-oxetane, and3-[ethyl-3[[(3-ethyloxetane-3-yl]methoxy]methyl]oxetane.

The crosslinking agent may be present in an amount of about 0.1 parts byweight to about 50 parts by weight, for example about 1 part by weightto about 30 parts by weight, or about 5 parts by weight to about 15parts by weight, based on 100 parts by weight of the siloxane resinrepresented by Formula 1. Within these ranges, the crosslinking agentcan improve the flexibility and hardness of the window film.

The composition for a window film according to embodiments may alsofurther include at least one of the nanoparticles and the additive,which are set forth above.

A flexible window film according to embodiments of the present inventionis depicted in FIG. 1. FIG. 1 is a schematic cross-sectional view of aflexible window film according to embodiments of the present invention.Referring to FIG. 1, a flexible window film 100 according to embodimentsof the present invention may include a base layer 110 and a coatinglayer 120, and the coating layer 120 may be formed of the compositionfor a window film according to embodiments of the present invention.

The base layer 110 supports the flexible window film 100 and the coatinglayer 120, thereby improving the mechanical strength of the flexiblewindow film 100. The base layer 110 may be attached to a display unit, atouchscreen panel, or a polarizing plate via an adhesive layer or thelike.

The base layer 110 may be formed of an optically transparent flexibleresin. For example, the resin may be selected from polyester resins suchas polyethylene terephthalate, polyethylene naphthalate, polybutyleneterephthalate, and polybutylene naphthalate; polycarbonate resins;polyimide resins; polystyrene resins; and poly(meth)acrylate resins suchas polymethyl methacrylate. A single one of these resins may be usedalone, or a combination thereof may be used. The base layer 110 may havea thickness of about 10 μm to about 200 μm, for example about 20 μm toabout 150 μm, or about 50 μm to about 100 μm. Within these ranges, thebase layer 110 can be used for a flexible window film.

The coating layer 120 is formed on the base layer 110 to protect thebase layer 110 and a display unit, a touchscreen panel or a polarizingplate, and can be used in flexible displays due to its high flexibilityand high hardness. The coating layer 120 may have a thickness of about 5μm to about 100 μm, for example about 10 μm to about 80 μm. Within theseranges, the coating layer 120 can be used in flexible window films.

Although not shown in FIG. 1, a functional layer, such as anantireflective layer, an anti-glare layer, and/or a hard coating layer,may be further formed on the other surface of the coating layer 120 toprovide an additional function to the flexible window film. In addition,although not shown in FIG. 1, the coating layer 120 may be furtherformed on the other surface of the base layer 110.

The flexible window film 100 is optically transparent and can be used intransparent displays. In some embodiments, the flexible window film 100may have a transmittance of about 88% or higher, for example about 88%to about 100%, in the visible light region, for example at a wavelengthof about 400 nm to about 800 nm. Within these ranges, the flexiblewindow film 100 can be used as a flexible window film.

The flexible window film 100 may have a pencil hardness of about 7H orhigher, a radius of curvature of about 5.0 mm or less, and ΔY.I. ofabout 5.0 or less. Within these ranges, the flexible window film 100 canbe used as a flexible window film due to its good hardness, flexibilityand light resistance. For example, the flexible window film 100 may havea pencil hardness of about 7H to about 9H, a radius of curvature ofabout 0.1 mm to about 5.0 mm, and ΔY.I. of about 0.1 to about 5.0.

The flexible window film 100 may have a thickness of about 50 μm toabout 300 μm. Within this range, the flexible window film 100 can beused as a flexible window film.

The flexible window film 100 may be manufactured by a method thatincludes coating the composition for a window film according toembodiments of the present invention onto the base layer 110, followedby curing the composition.

The method of coating the composition for a window film onto the baselayer 110 is not particularly limited. For example, the coating methodmay include bar coating, spin coating, dip coating, roll coating, flowcoating, die coating, or the like. The composition for a window film maybe coated onto the base layer 110 to a thickness of about 5 μm to about100 μm. Within this range, a desired coating layer can be obtained, andthe coating layer has good hardness, flexibility and reliability.

Curing allows the composition for a window film to be cured to form thecoating layer, and may include at least one of photocuring and/orthermal curing. Photocuring may include irradiating the composition withlight at a wavelength of about 400 nm or lower at a dose of about 10mJ/cm² to about 1000 mJ/cm². Thermal curing may include treating thecomposition at about 40° C. to about 200° C. for about 1 hour to about30 hours. Within these ranges, the composition for a window film can besufficiently cured. For example, the composition may be subjected tophotocuring, followed by thermal curing, thereby further improving thehardness of the coating layer.

After the composition is coated onto the base layer 110 and before thecomposition is cured, the method of manufacturing a flexible window filmmay further include drying the composition for a window film. Thecomposition may be dried, followed by curing, thereby preventing (orreducing) increases in the surface roughness of the coating layer due tophotocuring or thermal curing for a long period of time. Drying may beperformed at about 40° C. to about 200° C. for about 1 minute to about30 hours, but is not limited thereto.

A flexible window film according to embodiments of the present inventionis depicted in FIG. 2. FIG. 2 is a schematic cross-sectional view of aflexible window film according to embodiments of the present invention.Referring to FIG. 2, a flexible window film 200 according to embodimentsof the present invention may include a base layer 110, a coating layer120 formed on one surface of the base layer 110, and an adhesive layer130 formed on the other surface of the base layer 110. The coating layer120 may be formed of the composition for a window film according toembodiments of the present invention. The adhesive layer 130 is formedon the other surface of the base layer 110, thereby facilitating bondingbetween the flexible window film and a touchscreen panel, a polarizingplate or a display unit. This flexible window film 200 is substantiallythe same as the flexible window film 100 described above in connectionwith FIG. 1 except that the flexible window film 200 further includesthe adhesive layer. Thus, the adhesive layer will now be described.

The adhesive layer 130 bonds a polarizing plate, a touchscreen panel ora display unit (which may be disposed on a lower side of the flexiblewindow film 200) to the flexible window film 200, and may be formed of acomposition for adhesive layers. For example, the adhesive layer 130 maybe formed of a composition for adhesive layers, which includes anadhesive resin (such as a (meth)acrylic resin, a urethane resin, asilicone resin and/or an epoxy resin), a curing agent, a photoinitiator,and a silane coupling agent.

The (meth)acrylic resin may be a (meth)acrylic copolymer having an alkylgroup, a hydroxyl group, an aromatic group, a carboxylic acid group, analicyclic group, a heteroalicyclic group, and/or the like, and mayinclude any suitable (meth)acrylic copolymer(s). For example, the(meth)acrylic resin may be formed of a monomer mixture including atleast one of a (meth)acrylic monomer containing a C₁ to C₁₀unsubstituted alkyl group, a C₁ to C₁₀ alkyl group-containing(meth)acrylic monomer having at least one hydroxyl group, a C₆ to C₂₀aromatic group-containing (meth)acrylic monomer, a carboxylic acidgroup-containing (meth)acrylic monomer, a C₃ to C₂₀ alicyclicgroup-containing (meth)acrylic monomer, and/or a C₃ to C₁₀heteroalicyclic group-containing (meth)acrylic monomer having at leastone of nitrogen (N), oxygen (O) and sulfur (S).

The curing agent may be a polyfunctional (meth)acrylate, and may beselected from bifunctional (meth)acrylates such as hexanedioldiacrylate; trifunctional (meth)acrylates such as trimethylolpropanetri(meth)acrylate; tetrafunctional (meth)acrylates such aspentaerythritol tetra(meth)acrylate; pentafunctional (meth)acrylatessuch as dipentaerythritol penta(meth)acrylate; and hexafunctional(meth)acrylates such as dipentaerythritol hexa(meth)acrylate, but thecuring agent is not limited thereto.

The photoinitiator may be any suitable photoinitiator, and may includethe photo-radical initiators as set forth above.

The silane coupling agent may include an epoxy group-containing silanecoupling agent such as 3-glycidoxypropyltrimethoxysilane.

The composition for adhesive layers may include 100 parts by weight ofthe (meth)acrylic resin, about 0.1 parts by weight to about 30 parts byweight of the curing agent, about 0.1 parts by weight to about 10 partsby weight of the photoinitiator, and about 0.1 parts by weight to about20 parts by weight of the silane coupling agent. Within these ranges,the adhesive layer 130 allows the flexible window film to be efficientlybonded to the display unit, touchscreen panel, or polarizing plate.

The adhesive layer 130 may have a thickness of about 10 μm to about 100μm. Within this range, the adhesive layer 130 allows the flexible windowfilm to be sufficiently bonded to an optical device, such as apolarizing plate or the like.

A flexible display according to embodiments of the present invention isdepicted in FIGS. 3 and 4. FIG. 3 is a partial cross-sectional view of aflexible display according embodiments of the present invention, andFIG. 4 is a partial cross-sectional view of embodiments of a displayunit of the flexible display of FIG. 3. Referring to FIG. 3, a flexibledisplay 300 according to embodiments may include a display unit 350 a,an adhesive layer 360, a polarizing plate 370, a touchscreen panel 380,and a flexible window film 390. The flexible window film 390 may includethe flexible window film according to embodiments of the presentinvention.

The display unit 350 a drives the flexible display 300 and may include aboard and an optical device, such as an OLED, LED or LCD device, whichis formed on the board. FIG. 4 is a partial cross-sectional view ofembodiments of the display unit of the flexible display of FIG. 3.Referring to FIG. 4, the display unit 350 a may include a lower board310, a thin film transistor 316, an organic light emitting diode 315, aplanarization layer 314, a protective film 318, and an insulating film317.

The lower board 310 supports the display unit 350 a, and the thin filmtransistor 316 and the organic light emitting diode 315 may be formed onthe lower board 310. A flexible printed circuit board (FPCB) for drivingthe touchscreen panel 380 may be formed on the lower board 310. A timingcontroller, a power supply and the like for driving the organic lightemitting diode may be further formed on the flexible printed circuitboard.

The lower board 310 may include a board formed of a flexible resin. Forexample, the lower board 310 may include a silicone board, a polyimideboard, a polycarbonate board, or a polyacrylate board, but the lowerboard 310 is not limited thereto.

In the display region of the lower board 310, a plurality of pixelregions may be defined by intersecting a plurality of driving wires (notshown) with a plurality of sensor wires (not shown), and an organiclight emitting diode array including the thin film transistor 316 andthe organic light emitting diode 315 connected to the thin filmtransistor 316 may be formed in each of the pixel regions. In thenon-display region of the lower board 310, a gate driver for applying anelectrical signal to the driving wires may be formed in a gate-in-panelform. A gate-in-panel circuit may be formed at one or both sides of thedisplay region.

The thin film transistor 316 controls electric current, which flowsthrough a semiconductor upon application of an electric fieldperpendicular to the current to the semiconductor, and may be formed onthe lower board 310. The thin film transistor 316 may include a gateelectrode 310 a, a gate insulating film 311, a semiconductor layer 312,a source electrode 313 a, and a drain electrode 313 b. The thin filmtransistor 316 may be an oxide thin film transistor including an oxide(such as indium gallium zinc oxide (IGZO), ZnO, and/or TiO) as thesemiconductor layer 312, an organic thin film transistor including anorganic material as the semiconductor layer, an amorphous silicon thinfilm transistor including amorphous silicon as the semiconductor layer,or a polycrystalline silicon thin film transistor includingpolycrystalline silicon as the semiconductor layer.

The planarization layer 314 covers the thin film transistor 316 and acircuit 310 b to flatten the upper sides of the thin film transistor 316and the circuit 310 b, thereby allowing the organic light emitting diode315 to be formed. The planarization layer 314 may be formed of aspin-on-glass (SOG) film, a polyimide polymer, or a polyacrylic polymer,but is not limited thereto.

The organic light emitting diode 315 emits light to display an image,and may include a first electrode 315 a, an organic light emitting layer315 b and a second electrode 315 c, which are sequentially stacked, oneabove the other. Adjoining organic light emitting diodes may beseparated from each other by the insulating film 317. The organic lightemitting diode 315 may include a back side light emitting structure inwhich light generated in the organic light emitting layer 315 b isemitted through the lower board, or a front side light emittingstructure in which light generated in the organic light emitting layer315 b is emitted through the upper board.

The protective film 318 covers the organic light emitting diode 315 toprotect the organic light emitting diode 315. The protective film 318may be formed of an inorganic material (such as SiOx, SiNx, SiC, SiON,SiONC and amorphous carbon (a-C)), and an organic material (such as(meth)acrylates, epoxy polymers, and imide polymers). For example, theprotective film 318 may include an encapsulation layer in which a layerformed of an inorganic material and a layer formed of an organicmaterial are alternately stacked to form one or more dyads.

Referring again to FIG. 3, the display unit 350 a is bonded to thepolarizing plate 370 via the adhesive layer 360. The adhesive layer 360may be formed of an adhesive composition including a (meth)acrylateresin, a curing agent, an initiator and a silane coupling agent.

The polarizing plate 370 polarizes internal light or prevents reflectionof external light, thereby displaying an image or improving contrast ofthe displayed image. The polarizing plate may include a polarizer alone.Alternatively, the polarizing plate may include a polarizer and aprotective film formed on one or both surfaces of the polarizer.Alternatively, the polarizing plate may include a polarizer and aprotective coating layer formed on one or both surfaces of thepolarizer. The polarizer, the protective film and the protective coatinglayer may be any suitable polarizer, suitable protective film andsuitable protective coating layer known to those skilled in the art.

The touchscreen panel 380 generates an electrical signal by sensingchanges in capacitance generated when a human body or a conductor suchas a stylus touches the touchscreen panel, and the display unit 350 amay be driven by the signal. The touchscreen panel 380 is formed bypatterning a flexible conductor, and may include first sensorelectrodes, and second sensor electrodes each formed between the firstsensor electrodes and intersecting the first sensor electrodes. Theconductor for the touchscreen panel 380 may include metal nanowires,conductive polymers, and/or carbon nanotubes, but is not limitedthereto.

The flexible window film 390 may be formed at an outermost side of theflexible display 300 to protect the display.

Although not shown in FIG. 3, an adhesive layer may be further formedbetween the polarizing plate 370 and the touchscreen panel 380 and/orbetween the touchscreen panel 380 and the flexible window film 390,thereby reinforcing bonding between the polarizing plate, thetouchscreen panel, and the flexible window film. The adhesive layer maybe formed of an adhesive composition including a (meth)acrylate resin, acuring agent, an initiator, and a silane coupling agent. Although notshown in FIG. 3, a polarizing plate may be further formed on a lowerside of the display unit 350 a, thereby enabling polarization ofinternal light.

A flexible display according to embodiments of the present invention isdepicted in FIG. 5. FIG. 5 is a partial cross-sectional view of aflexible display according to embodiments of the present invention.Referring to FIG. 5, a flexible display 400 according to embodiments ofthe present invention may include a display unit 350 a, a touchscreenpanel 380, a polarizing plate 370, and a flexible window film 390. Theflexible window film 390 may include the flexible window film accordingto embodiments of the present invention. The flexible display 400depicted in FIG. 5 is substantially the same as the flexible displaysdescribed above except that the touchscreen panel 380 is not formeddirectly on the flexible window film 390, and is formed on a lower sideof the polarizing plate 370. Here, the touchscreen panel 380 may beformed together with the display unit 350 a. In this case, thetouchscreen panel 380 is formed integrally with the display unit 350 a,enabling the flexible display 400 to have a thinner thickness and higherbrightness, and thus better visibility than the flexible displaysdescribed above. In addition, the touchscreen panel 380 may be formed bydeposition, although it is not limited thereto. Although not shown inFIG. 5, an adhesive layer may be further formed between the display unit350 a and the touchscreen panel 380, between the touchscreen panel 380and the polarizing plate 370, and/or between the polarizing plate 370and the flexible window film 390, thereby improving the mechanicalstrength of the display. The adhesive layer may be formed of an adhesivecomposition including a (meth)acrylate resin, a curing agent, aninitiator, and a silane coupling agent. Although not shown in FIG. 5, apolarizing plate may be further formed on a lower side of the displayunit 350 a, thereby improving the displayed image by polarizing internallight.

A flexible display according to embodiments of the present invention isdepicted in FIG. 6. FIG. 6 is a partial cross-sectional view of aflexible display according to embodiments of the present invention.Referring to FIG. 6, a flexible display 500 according to embodiments ofthe present invention may include a display unit 350 b, an adhesivelayer 360, and a flexible window film 390. The flexible window film 390may include the flexible window film according to embodiments of thepresent invention. The flexible display 500 is substantially the same asthe flexible displays described above except that the display can bedriven only by the display unit 350 b, and the polarizing plate andtouchscreen panel are omitted.

The display unit 350 b may include a board and an optical device (suchas an LCD, OLED or LED device) formed on the board. In addition, thedisplay unit 350 b may include a touchscreen panel therein.

Next, embodiments of the present invention will be described withreference to some examples. It is understood, however, that theseexamples are provided for illustration only and are not to be construedin any way as limiting the embodiments of the present invention.

Example 1

50 g of a monomer mixture including 95 mol % of2-(3,4-epoxycyclohexyl)ethyltriethoxysilane (Sigma-Aldrich Co., Ltd.)and 5 mol % of 2-(3,4-epoxycyclohexyl)ethylmethyldiethoxysilane (GelestCo., Ltd.) were placed in a 200 ml 2-neck flask. Based on the amount ofthe monomer mixture, 2 mol % of KOH and 1 mol % of water were added tothe monomer mixture, followed by stirring at 65° C. for 4 hours. Asiloxane resin (weight average molecular weight measured by gelpermeation chromatography (GPC): 6200) was prepared by removing residualwater and alcohol using a vacuum distillation apparatus, followed byadding methylethylketone to the mixture, thereby adjusting the amount ofthe siloxane resin to 90% by weight (wt %) in terms of solids content.

100 parts by weight of the prepared siloxane resin, 5 parts by weight ofIrgacure-250 (BASF Co., Ltd.) as an initiator, and 1 part by weight ofTinuvin 479 (BASF Co., Ltd.) as a UV absorber were mixed, therebypreparing a composition for a window film. The prepared composition wascoated onto a polyethylene terephthalate film (TA043, Toyobo Co., Ltd.,thickness: 80 μm), followed by drying at 100° C. for 5 minutes. Next,the composition was subjected to UV irradiation at a dose of 1000mJ/cm², followed by heating at 80° C. for 4 hours, thereby manufacturinga window film including a 50 μm thick coating layer.

Example 2

50 g of a monomer mixture including 95 mol % of2-(3,4-epoxycyclohexyl)ethyltriethoxysilane (Sigma-Aldrich Co., Ltd.)and 5 mol % of 2-(3,4-epoxycyclohexyl)ethylmethyldiethoxysilane (GelestCo., Ltd.) were placed in a 200 ml 2-neck flask. Based on the amount ofthe monomer mixture, 2 mol % of KOH and 1 mol % of water were added tothe monomer mixture, followed by stirring at 65° C. for 4 hours. Asiloxane resin (weight average molecular weight measured by GPC: 6200)was prepared by removing residual water and alcohol using a vacuumdistillation apparatus, followed by adding methylethylketone to themixture, thereby adjusting the amount of the siloxane resin to 90 wt %in terms of solids content.

100 parts by weight of the prepared siloxane resin, 10 parts by weightof CY-179 (CIBA Co., Ltd.) as a crosslinking agent, 5 parts by weight ofIrgacure-250 (BASF Co., Ltd.) as an initiator, and 1 part by weight ofTinuvin 479 (BASF Co., Ltd.) as a UV absorber were mixed, therebypreparing a composition for a window film. The prepared composition wascoated onto a polyethylene terephthalate film (TA043, Toyobo Co., Ltd.,thickness: 80 μm), followed by drying at 100° C. for 5 minutes. Next,the composition was subjected to UV irradiation at a dose of 1000mJ/cm², followed by heating at 80° C. for 4 hours, thereby manufacturinga window film including a 50 μm thick coating layer.

Example 3

50 g of a monomer mixture including 90 mol % of2-(3,4-epoxycyclohexyl)ethyltriethoxysilane (Sigma-Aldrich Co., Ltd.)and 10 mol % of 2-(3,4-epoxycyclohexyl)ethylmethyldiethoxysilane (GelestCo., Ltd.) were placed in a 200 ml 2-neck flask. Based on the amount ofthe monomer mixture, 2 mol % of KOH and 1 mol % of water were added tothe monomer mixture, followed by stirring at 65° C. for 4 hours. Asiloxane resin (weight average molecular weight measured by GPC: 6200)was prepared by removing residual water and alcohol using a vacuumdistillation apparatus, followed by adding methylethylketone to themixture, thereby adjusting the amount of the siloxane resin to 90 wt %in terms of solids content. A window film was manufactured as in Example2 using the prepared siloxane resin.

Example 4

50 g of a monomer mixture including 95 mol % of2-(3,4-epoxycyclohexyl)ethyltriethoxysilane (Sigma-Aldrich Co., Ltd.)and 5 mol % of dimethyldimethoxysilane (Sigma-Aldrich Co., Ltd.) wereplaced in a 200 ml 2-neck flask. Based on the amount of the monomermixture, 2 mol % of KOH and 1 mol % of water were added to the monomermixture, followed by stirring at 65° C. for 4 hours. A siloxane resin(weight average molecular weight measured by GPC: 6200) was prepared byremoving residual water and alcohol using a vacuum distillationapparatus, followed by adding methylethylketone to the mixture, therebyadjusting the amount of the siloxane resin to 90 wt % in terms of solidscontent. A window film was manufactured as in Example 2 using theprepared siloxane resin.

Example 5

50 g of a monomer mixture including 90 mol % of2-(3,4-epoxycyclohexyl)ethyltriethoxysilane (Sigma-Aldrich Co., Ltd.)and 10 mol % of dimethyldimethoxysilane (Sigma-Aldrich Co., Ltd.) wereplaced in a 200 ml 2-neck flask. Based on the amount of the monomermixture, 2 mol % of KOH and 1 mol % of water were added to the monomermixture, followed by stirring at 65° C. for 4 hours. A siloxane resin(weight average molecular weight measured by GPC: 6200) was prepared byremoving residual water and alcohol using a vacuum distillationapparatus, followed by adding methylethylketone to the mixture, therebyadjusting the amount of the siloxane resin to 90 wt % in terms of solidscontent. A window film was manufactured as in Example 2 using theprepared siloxane resin.

Example 6

50 g of a monomer mixture including 90 mol % of2-(3,4-epoxycyclohexyl)ethyltriethoxysilane (Sigma-Aldrich Co., Ltd.), 5mol % of 2-(3,4-epoxycyclohexyl)ethylmethyldiethoxysilane (Gelest Co.,Ltd.) and 5 mol % of dimethyldimethoxysilane (Sigma-Aldrich Co., Ltd.)were placed in a 200 ml 2-neck flask. Based on the amount of the monomermixture, 2 mol % of KOH and 1 mol % of water were added to the monomermixture, followed by stirring at 65° C. for 4 hours. A siloxane resin(weight average molecular weight measured by GPC: 6200) was prepared byremoving residual water and alcohol using a vacuum distillationapparatus, followed by adding methylethylketone to the mixture, therebyadjusting the amount of the siloxane resin to 90 wt % in terms of solidscontent. A window film was manufactured as in Example 2 using theprepared siloxane resin.

Example 7

A window film was manufactured as in Example 4, except that 10 parts byweight of diglycidyl 1,2-cyclohexanedicarboxylate (Sigma-Aldrich Co.,Ltd.) was used as the crosslinking agent instead of the 10 parts byweight of CY-179 (CIBA Co., Ltd.).

Comparative Example 1

50 g of a monomer mixture including 100 mol % of2-(3,4-epoxycyclohexyl)ethyltriethoxysilane (Sigma-Aldrich Co., Ltd.)were placed in a 200 ml 2-neck flask. Based on the amount of the monomermixture, 2 mol % of KOH and 1 mol % of water were added to the monomermixture, followed by stirring at 65° C. for 4 hours. A siloxane resin(weight average molecular weight measured by GPC: 6200) was prepared byremoving residual water and alcohol using a vacuum distillationapparatus, followed by adding methylethylketone to the mixture, therebyadjusting the amount of the siloxane resin to 90 wt % in terms of solidscontent. A window film was manufactured as in Example 2 using theprepared siloxane resin.

Comparative Example 2

50 g of a monomer mixture including 100 mol % of3-glycidoxypropyltriethoxysilane (Gelest Co., Ltd.) were placed in a 200ml 2-neck flask. Based on the amount of the monomer mixture, 2 mol % ofKOH and 1 mol % of water were added to the monomer mixture, followed bystirring at 65° C. for 4 hours. A siloxane resin (weight averagemolecular weight measured by GPC: 6200) was prepared by removingresidual water and alcohol using a vacuum distillation apparatus,followed by adding methylethylketone to the mixture, thereby adjustingthe amount of the siloxane resin to 90 wt % in terms of solids content.A window film was manufactured as in Example 2 using the preparedsiloxane resin.

Comparative Example 3

50 g of a monomer mixture including 95 mol % of2-(3,4-epoxycyclohexyl)ethyltriethoxysilane (Sigma-Aldrich Co., Ltd.)and 5 mol % of phenylmethyldimethoxysilane (Gelest Co., Ltd.) wereplaced in a 200 ml 2-neck flask. Based on the amount of the monomermixture, 2 mol % of KOH and 1 mol % of water were added to the monomermixture, followed by stirring at 65° C. for 4 hours. A siloxane resin(weight average molecular weight measured by GPC: 6200) was prepared byremoving residual water and alcohol using a vacuum distillationapparatus, followed by adding methylethylketone to the mixture, therebyadjusting the amount of the siloxane resin to 90 wt % in terms of solidcontents. A window film was manufactured as in Example 2 using theprepared siloxane resin.

Comparative Example 4

50 g of a monomer mixture including 100 mol % of2-(3,4-epoxycyclohexyl)ethylmethyldiethoxysilane (Sigma-Aldrich Co.,Ltd.) were placed in a 200 ml 2-neck flask. Based on the amount of themonomer mixture, 2 mol % of KOH and 1 mol % of water were added to themonomer mixture, followed by stirring at 65° C. for 4 hours. A siloxaneresin (weight average molecular weight measured by GPC: 6200) wasprepared by removing residual water and alcohol using a vacuumdistillation apparatus, followed by adding methylethylketone to themixture, thereby adjusting the amount of the siloxane resin to 90 wt %in terms of solids content. A window film was manufactured as in Example2 using the prepared siloxane resin.

Comparative Example 5

50 g of a monomer mixture including 95 mol % of methyltrimethoxysilaneand 5 mol % of 2-(3,4-epoxycyclohexyl)ethylmethyldiethoxysilane(Sigma-Aldrich Co., Ltd.) were placed in a 200 ml 2-neck flask. Based onthe amount of the monomer mixture, 2 mol % of KOH and 1 mol % of waterwere added to the monomer mixture, followed by stirring at 65° C. for 4hours. A siloxane resin (weight average molecular weight measured byGPC: 6200) was prepared by removing residual water and alcohol using avacuum distillation apparatus, followed by adding methylethylketone tothe mixture, thereby adjusting the amount of the siloxane resin to 90 wt% in terms of solids content. A window film was manufactured as inExample 2 using the prepared siloxane resin.

Comparative Example 6

50 g of a monomer mixture including 95 mol % of methyltrimethoxysilaneand 5 mol % of 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane(Sigma-Aldrich Co., Ltd.) were placed in a 200 ml 2-neck flask. Based onthe amount of the monomer mixture, 2 mol % of KOH and 1 mol % of waterwere added to the monomer mixture, followed by stirring at 65° C. for 4hours. A siloxane resin (weight average molecular weight measured byGPC: 6200) was prepared by removing residual water and alcohol using avacuum distillation apparatus, followed by adding methylethylketone tothe mixture, thereby adjusting the amount of the siloxane resin to 90 wt% in terms of solids content. A window film was manufactured as inExample 2 using the prepared siloxane resin.

The details of the compositions for a window film referenced in theExamples and Comparative Examples are shown in Tables 1 and 2. Thewindow films manufactured according to the Examples and ComparativeExamples were evaluated as to the following properties (1) to (3). Theresults are shown in Tables 1 and 2.

(1) Pencil hardness: Pencil hardness was measured on the coating layerof the window film using a pencil hardness tester (Heidon Co., Ltd.) inaccordance with JIS K5400. A pencil (Mitsubishi Co., Ltd.) having apencil hardness of 6B to 9H was used. Pencil hardness was measured undera load of 1 kg on the coating layer, a scratching angle of 45°, and ascratching speed of 60 mm/min. When the coating layer had one or morescratches after being tested 5 times using a certain pencil, the pencilhardness was measured again using another pencil having one-level lowerhardness than the previous pencil. The maximum pencil hardness value ofthe pencil that allowed no scratches to be observed after repeating thepencil hardness measurement five times on the coating layer was taken asthe pencil hardness of the coating layer.

(2) Radius of curvature: The window film (width×length×thickness: 3cm×15 cm×130 μm, base layer thickness: 80 μm, coating layer thickness:50 μm) was wound around a jig for testing radius of curvature, followedby keeping the window film wound for 5 seconds, and then unwinding thefilm from the jig. Next, the window film was observed by the naked eyeas to whether the window film suffered from cracking. Here, the radiusof curvature in the compressive direction was measured when the windowfilm was wound around the jig such that the coating layer of the windowfilm contacted the jig. The radius of curvature in the tensile directionwas measured when the window film was wound around the jig such that thebase layer of the window film contacted the jig. Measurement of theradius of curvature in the compressive direction was performed while thediameter of the jig was gradually decreased from a maximum diameter, andthe minimum radius of the jig causing no observable cracks in the windowfilm was recorded as the radius of curvature of the window film.

(3) Light resistance reliability: The yellow index (Y1) of the windowfilm was measured under a D65 light source and a 2° angle between thewindow film and the light source using a colorimeter (CM3600D, KonicaMinolta Co., Ltd.). Then, the window film was irradiated with lighthaving a peak wavelength of 306 nm for 72 hours using a light resistancetester (Xe-1, Q-sun Co., Ltd.), followed by measuring the yellow index(Y2) in the same manner as described above. The light resistance of thewindow film was determined by the difference in the yellow index beforeand after light irradiation (i.e., ΔY.I.=Y2-Y1,).

TABLE 1 Example 1 2 3 4 5 6 7 Silicone2-(3,4-epoxycyclohexyl)ethyltriethoxysilane 95 95 90 95 90 90 95 monomer2-(3,4- 5 5 10 — — 5 — (mol %) epoxycyclohexyl)ethylmethyldiethoxysilaneDimethyldimethoxysilane — — — 5 10 5 5 Phenylmethyldimethoxysilane — — —— — — — 3-glycidoxypropyltriethoxysilane — — — — — — —Methyltrinnethoxysilane — — — — — — — Crosslinking agent (parts byweight) — 10 10 10 10 10 10 Initiator (parts by weight) 5 5 5 5 5 5 5 UVabsorber (parts by weight) 1 1 1 1 1 1 1 Pencil hardness 7H 8H 7H 8H 7H7H 8H Radius of curvature (mm) 3.8 3.0 2.8 3.1 2.6 2.7 3.8 Lightresistance reliability 2.5 2.8 2.6 2.4 2.3 2.5 2.2

TABLE 2 Comparative Example 1 2 3 4 5 6 Silicone2-(3,4-epoxycyclohexyl)ethyltriethoxysilane 100 — 95 — — 5 monomer2-(3,4- — — — 100 5 — (mol %) epoxycyclohexyl)ethylmethyldiethoxysilaneDimethyldimethoxysilane — — — — — — Phenylmethyldimethoxysilane — — 5 —— — 3-glycidoxypropyltriethoxysilane — 100 — — — —Methyltrimethoxysilane — — — — 95 95 Crosslinking agent (parts byweight) 10 10 10 10 10 10 Initiator (parts by weight) 5 5 5 5 5 5 UVabsorber (parts by weight) 1 1 1 1 1 1 Pencil hardness 7H 6H 6H 2H 3H 4HRadius of curvature (mm) 5.9 4.6 6.9 2.0 7.6 8.2 Light resistancereliability 3.8 5.2 9.7 3.5 3.9 3.9

As shown in Table 1, since the window films according to embodiments ofthe present invention had high hardness (such as a pencil hardness of 7Hor higher), good flexibility (such as a radius of curvature of 5.0 mm orless), and good light resistance reliability, the window films accordingto embodiments of the present invention could be used as flexible windowfilms.

According to embodiments of the present invention, a composition for awindow film can be used to make a flexible window film having goodhardness and flexibility. According to embodiments of the presentinvention, a flexible window film has good hardness and flexibility, anda flexible display includes the flexible window film.

However, as shown in Table 2, the window films of Comparative Examples 1to 6 (including the coating layer which did not include the siloxaneresin according to embodiments of the present invention) had poorerpencil hardness, radius of curvature and/or light resistance than thewindow films according to embodiments of the present invention.

While certain embodiments of the present invention have been illustratedand described, it is understood that various modifications, changes,alterations, and equivalent embodiments can be made by those skilled inthe art without departing from the spirit and scope of the invention, asdefined in the following claims.

What is claimed is:
 1. A composition for a window film, comprising: asiloxane resin represented by Formula 1; and an initiator,(R¹SiO_(3/2))_(x)(R²R³SiO_(2/2))_(y)  Formula 1 wherein: R¹ is acrosslinkable functional group; R² and R³ are each independentlyhydrogen, a crosslinkable functional group, an unsubstituted orsubstituted C₁ to C₂₀ alkyl group, or an unsubstituted or substituted C₅to C₂₀ cycloalkyl group; at least one of R² and R³ is an unsubstitutedor substituted C₁ to C₂₀ alkyl group; 0<x<1; 0<y<1; and x+y=1.
 2. Thecomposition according to claim 1, wherein the siloxane resin comprises acompound represented by one of Formulae 1-1 to 1-18:(EcSiO_(3/2))_(x)(EcMeSiO_(2/2))_(y)  Formula 1-1(EcSiO_(3/2))_(x)((Me)₂SiO_(2/2))_(y)  Formula 1-2(EcSiO_(3/2))_(x)(GpMeSiO_(2/2))_(y)  Formula 1-3(GpSiO_(3/2))_(x)(EcMeSiO_(2/2))_(y)  Formula 1-4(GpSiO_(3/2))_(x)((Me)₂SiC_(2/2))_(y)  Formula 1-5(GpSiO_(3/2))_(x)(GpMeSiO_(2/2))_(y)  Formula 1-6(OpSiO_(3/2))_(x)(EcMeSiO_(2/2))_(y)  Formula 1-7(OpSiO_(3/2))_(x)((Me)₂SiO_(2/2))_(y)  Formula 1-8(OpSiO_(3/2))_(x)(GpMeSiO_(2/2))_(y)  Formula 1-9 wherein, in Formulae1-1 through 1-9, Ec is a (3,4-epoxycyclohexyl)ethyl group; Me is amethyl group; Gp is a 3-glycidoxypropyl group; Op is a 3-oxetanylpropylgroup; 0<x<1; 0<y<1; and x+y=1;(EcSiO_(3/2))_(x)(EcMeSiO_(2/2))_(yl)((Me)₂SiO_(2/2))_(y2)  Formula 1-10(GpSiO_(3/2))_(x)(EcMeSiO_(2/2))_(y1)((Me)₂SiO_(2/2))_(y2)  Formula 1-10(OpSiO_(3/2))_(x)(EcMeSiO_(2/2))_(y1)((Me)₂SiO_(2/2))_(y2)  Formula 1-12(EcSiO_(3/2))_(x)(GpMeSiO_(2/2))_(yl)((Me)₂SiO_(2/2))_(y2)  Formula 1-13(GpSiO_(3/2))_(x)(GpMeSiO_(2/2))_(yl)((Me)₂SiO_(2/2))_(y2)  Formula 1-14(OpSiO_(3/2))_(x)(GpMeSiO_(2/2))_(y1)((Me)₂SiO_(2/2))_(y2)  Formula 1-15(EcSiO_(3/2))_(x)(EcMeSiO_(2/2))_(yl)(GpMeSiO_(2/2))_(y2)  Formula 1-16(GpSiO_(3/2))_(x)(EcMeSiO_(2/2))_(yl)(GpMeSiO_(2/2))_(y2)  Formula 1-17(OpSiO_(3/2))_(x)(EcMeSiO_(2/2))_(yl)(GpMeSiO_(2/2))_(y2)  Formula 1-18wherein, in Formulae 1-10 through 1018, Ec is a(3,4-epoxycyclohexyl)ethyl group; Me is a methyl group; Gp is a3-glycidoxypropyl group; Op is a 3-oxetanylpropyl group; 0<x<1; 0<y1<1;0<y2<1; and x+y1+y2=1.
 3. The composition according to claim 1, furthercomprising: a crosslinking agent.
 4. The composition according to claim3, wherein the crosslinking agent is selected from the group consistingof non-cyclic aliphatic epoxy monomers, cyclic aliphatic epoxy monomers,aromatic epoxy monomers, hydrogenated aromatic epoxy monomers, oxetanemonomers, and combinations thereof.
 5. A flexible window film,comprising: a base layer; and a coating layer on a surface of the baselayer, the coating layer being formed from the composition according toclaim
 1. 6. The flexible window film according to claim 5, furthercomprising: an adhesive layer on an other surface of the base layer. 7.The flexible window film according to claim 5, wherein the flexiblewindow film has a pencil hardness of about 7H or higher, a radius ofcurvature of about 5.0 mm or lower, and a difference in yellow indexbefore and after irradiation (ΔY.I.) of about 5.0 or less.
 8. A flexibledisplay comprising the flexible window film according to claim
 5. 9. Theflexible display according to claim 8, comprising: a display unit; anadhesive layer on the display unit; a polarizing plate on the adhesivelayer; a touchscreen panel on the polarizing plate; and the flexiblewindow film on the touchscreen panel.
 10. The flexible display accordingto claim 8, comprising: a display unit; a touchscreen panel on thedisplay unit; a polarizing plate on the touchscreen panel; and theflexible window film on the polarizing plate.
 11. The flexible displayaccording to claim 8, comprising: a display unit; an adhesive layer onthe display unit; and the flexible window film on the adhesive layer.12. The flexible display according to claim 11, further comprising: apolarizing plate on an upper or lower side of the display unit.